arXiv 1010.30752010-10-15cond-mat.stat-mech

二维XY模型中的Berezinskiii-Kosterlitz-Thouless型渗流相变

Berezinskii-Kosterlitz-Thouless-like percolation transitions in the two-dimensional XY model

Hao Hu, Youjin Deng, Henk W. J. Blöte

备注：: 23 pages, 14 figures
发表信息：: PhysRevE.83.011124 (2011)
DOI：: 10.1103/PhysRevE.83.011124

摘要：

本文用蒙特卡罗方法研究了二维XY自旋组态衬底上的渗流问题。对于一个给定的自旋配置，我们构建渗流集团随机选择一个方向$x$在自旋向量空间，然后放置一个最近的邻居网站$i$和$j$之间的概率$p_{ij} = \max (0,1-e^{-2K s^x_i s^x_j})$，其中$K > 0$控制的渗流过程的渗流键。在低温范围$J \geq J_{\rm c}$中发现了一条渗流阈值线$K_{\rm c} (J)$，其中$J > 0$是XY耦合强度。相关函数$g_p (r)$的分析，定义为概率，两个网站分开的距离$r$属于同一个渗流集群，产生代数衰减$K \geq K_{\rm c}(J)$，和相关的临界指数依赖于$J$和$K$。沿着阈值线$K_{\rm c}(J)$，在数值不确定性内，$g_p$的缩放维数等于$1/8$。在此基础上，我们推测沿$K_{\rm c} (J)$线的逾渗相变是Berezinskiii-Kosterlitz-无边界型的。

英文摘要：

We study a percolation problem on a substrate formed by two-dimensional XY spin configurations, using Monte Carlo methods. For a given spin configuration we construct percolation clusters by randomly choosing a direction $x$ in the spin vector space, and then placing a percolation bond between nearest-neighbor sites $i$ and $j$ with probability $p_{ij} = \max (0,1-e^{-2K s^x_i s^x_j})$, where $K > 0$ governs the percolation process. A line of percolation thresholds $K_{\rm c} (J)$ is found in the low-temperature range $J \geq J_{\rm c}$, where $J > 0$ is the XY coupling strength. Analysis of the correlation function $g_p (r)$, defined as the probability that two sites separated by a distance $r$ belong to the same percolation cluster, yields algebraic decay for $K \geq K_{\rm c}(J)$, and the associated critical exponent depends on $J$ and $K$. Along the threshold line $K_{\rm c}(J)$, the scaling dimension for $g_p$ is, within numerical uncertainties, equal to $1/8$. On this basis, we conjecture that the percolation transition along the $K_{\rm c} (J)$ line is of the Berezinskii-Kosterlitz-Thouless type.

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